Semiconductor wafer evaluation method and semiconductor wafer

ABSTRACT

A method of evaluating a semiconductor wafer, which has a polished surface, by using a laser surface-inspection device including light-incident and light-receiving systems, includes evaluating the semiconductor wafer by detecting, as a light point defect, an abnormality of a process-induced defect and a surface-adhered foreign matter present on the polished surface of the semiconductor wafer, on the basis of measurement result obtained by directing incident light to the polished surface of the semiconductor wafer from one light-incident system and receiving, with a first light-receiving system, radiation light which has been radiated by the incident light being reflected or scattered by the polished surface, measurement result obtained by receiving the radiation light with a second light-receiving system, and measurement result obtained by receiving the radiation light with a third light-receiving system, and at least one of a light-receiving angle and polarization selectivity differs among the first, second and third light-receiving systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 15/765,857, filed on Apr. 4, 2018, which is aNational Phase application of International Application No.PCT/JP2016/074471, filed on Aug. 23, 2016, which claims the benefit ofpriority to Japanese Patent Application No. 2015-199111 filed on Oct. 7,2015, the disclosure of each of which is expressly incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The present invention relates to a semiconductor wafer evaluationmethod, and more specifically relates to a method of evaluating asemiconductor wafer having a polished surface.

The present invention further relates to a semiconductor wafer which hasa polished surface and has been evaluated by the above evaluationmethod.

BACKGROUND ART

As the evaluation method for a defect of a semiconductor wafer or for aforeign matter adhering to the surface of a semiconductor wafer, amethod based on a light point defect (LPD) detected by a lasersurface-inspection device is widely used (for example, see JapanesePatent No. 5509581, which is expressly incorporated herein by referencein its entirety). In this method, light is directed to the surface of asemiconductor wafer to be evaluated, and the radiation light (scatteringlight and reflection light) from this surface is detected to evaluatethe presence or absence and/or size of a defect/foreign matter of thesemiconductor wafer.

SUMMARY OF THE INVENTION

Among semiconductor wafers, a polished wafer is a semiconductor waferwhich is produced through various types of steps including a polishingstep, and the surface (uppermost surface) thereof is a polished surface.Here, the polished surface means a surface on which mirror polishing(referred to also as mirror finish) has been performed. On the surface(polished surface) of a polished wafer, there may be a surface-adheredforeign matter and a defect (hereinafter, referred to as a“process-induced defect”) generated due to mirror polishing and/orvarious types of steps performed before/after the mirror polishing. Ifthese surface-adhered foreign matter and process-induced defect can bedetected, a polished wafer having few process-induceddefects/surface-adhered foreign matters can be provided by controllingthe manufacturing process, such as by removing the causes of thesurface-adhered foreign matter and process-induced defect on the basisof the detection result.

An aspect of the present invention provides for a new evaluation methodfor evaluating a semiconductor wafer having a polished surface bydetecting process-induced defects/surface-adhered foreign matters.

A laser surface-inspection device includes an incident system and alight-receiving system. In this connection, Japanese Patent No. 5509581describes an approach of detecting defects and foreign mattersintroduced in the polishing step by using a laser surface-inspectiondevice provided with two types of incident systems.

In contrast, the present inventor has newly discovered, as the resultsof repeating intensive studies, the following evaluation method usingincident light from one incident system:

a method of evaluating a semiconductor wafer having a polished surfaceby using a laser surface-inspection device including incident andlight-receiving systems, which includes evaluating the semiconductorwafer by detecting, as a light point defect, an abnormality selectedfrom the group consisting of a process-induced defect and asurface-adhered foreign matter present on the polished surface of thesemiconductor wafer, on the basis of measurement result 1 obtained bydirecting incident light to the polished surface of the semiconductorwafer from one incident system and receiving, with a firstlight-receiving system, radiation light which has been radiated by theincident light being reflected or scattered by the polished surface,measurement result 2 obtained by receiving the radiation light with asecond light-receiving system, and measurement result 3 obtained byreceiving the radiation light with a third light-receiving system,wherein at least one selected from the group consisting of alight-receiving angle and polarization selectivity differs among thefirst light-receiving system, the second light-receiving system, and thethird light-receiving system.

That is, with the above evaluation method, it is possible to detect theabove abnormalities on the basis of three types of measurement resultsobtained by a laser surface-inspection device including one incidentsystem and three types of light-receiving systems among which at leastone selected from the group consisting of a light-receiving angle andpolarization selectivity differs from each other.

In an embodiment, among the above three light-receiving systems, onelight-receiving system receives omnidirectional light, while each of theother two light-receiving systems selectively receives polarized lighthaving a different azimuth angle.

In an embodiment, the light-receiving angle of the light-receivingsystem which receives the omnidirectional light is a higher angle thanthe light-receiving angles of the other two light-receiving systems.

In an embodiment, when the azimuth angle of the polarized light receivedby one of the above other two light-receiving systems is designated byθ₁°, and the azimuth angle of the polarized light received by anotherone is designated by θ₂°, 0°≤θ₁°≤90° and 90°≤θ₂°≤180° are satisfied.

In an embodiment, the first light-receiving system receivesomnidirectional light,

the second light-receiving system receives polarized light havingazimuth angle θ₁°, and

the third light-receiving system receives polarized light having azimuthangle θ₂°, wherein

the light-receiving angle of the first light-receiving system is ahigher angle than the light-receiving angles of the secondlight-receiving system and third light-receiving system, and

on the basis of the determination criteria selected from the groupconsisting of the presence or absence of detection and detection size inthe measurement result 1, the presence or absence of detection anddetection size in the measurement result 2, and the presence or absenceof detection and detection size in the measurement result 3, it isdetermined whether the detected abnormality is a process-induced defector a surface-adhered foreign matter.

In an embodiment, the above determination is performed according to thedetermination criteria shown in Table 1 described later.

In the above determination criteria, 1.0<X<2.0 is satisfied. In anembodiment, 1.3<X<1.6 is satisfied.

In an embodiment, the incident angle of the above incident light ishigher than 0° and less than 90° when all the directions horizontal tothe polished surface of a semiconductor wafer are defined as 0° and thedirection perpendicular to the polished surface as 90°.

An aspect of the present invention relates to a semiconductor wafer,which has a polished surface and has been evaluated by the aboveevaluation method.

According to an aspect of the present invention, various types ofabnormalities of a semiconductor wafer having a polished surface can bedetected.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example (schematic configuration diagram) of alaser surface-inspection device.

FIG. 2 illustrates various types of abnormalities (SEM images) observedwith a scanning electron microscope on the polished surface of apolished wafer evaluated in Examples.

FIG. 3 is a graph illustrating the evaluation results of a polishedwafer with a laser surface-inspection device in Examples.

FIG. 4 is a graph illustrating the evaluation results of a polishedwafer with a laser surface-inspection device in Examples.

MODES FOR CARRYING OUT THE INVENTION

[Method of Evaluating Semiconductor Wafer]

An aspect of the present invention relates to a method (hereinafter,referred to also as “evaluation method”) of evaluating a semiconductorwafer having a polished surface by using a laser surface-inspectiondevice including incident and light-receiving systems. The aboveevaluation method includes evaluating the semiconductor wafer bydetecting, as a light point defect, an abnormality selected from thegroup consisting of a process-induced defect and a surface-adheredforeign matter present on the polished surface of the semiconductorwafer, on the basis of measurement result 1 obtained by directingincident light to the polished surface of the semiconductor wafer fromone incident system and receiving, with a first light-receiving system,radiation light which has been radiated by the incident light beingreflected or scattered by the polished surface, measurement result 2obtained by receiving the radiation light with a second light-receivingsystem, and measurement result 3 obtained by receiving the radiationlight with a third light-receiving system, and at least one selectedfrom the group consisting of a light-receiving angle and polarizationselectivity differs among the first light-receiving system, the secondlight-receiving system, and the third light-receiving system.

Hereinafter, the above evaluation method will be described in moredetail. In the followings, a semiconductor wafer having a polishedsurface will be referred to also as a polished wafer.

<Laser Surface-Inspection Device>

A laser surface-inspection device (hereinafter, simply referred to alsoas “surface inspection device”) used in the above evaluation methodincludes:

one incident system; and

three light-receiving systems (first light-receiving system, secondlight-receiving system, and third light-receiving system) among which atleast one selected from the group consisting of a light-receiving angleand polarization selectivity differs from each other.

In such a surface inspection device, the radiation light which has beenradiated by the light incident on the polished surface of thesemiconductor wafer to be evaluated being reflected or scattered atvarious places on the polished surface is received by the above threelight-receiving systems. The direction in which the radiation light isradiated (specifically, the reflection angle of reflection light or thescattering angle of scattering light) and the polarizationcharacteristic may variously vary with the presence of a process-induceddefect and/or surface-adhered foreign matter. The present inventorassumes that by receiving various radiation lights having differentradiation directions and polarization characteristics with the threelight-receiving systems among which at least one selected from the groupconsisting of a light-receiving angle and polarization selectivitydiffers from each other, a process-induced defect and/or surface-adheredforeign matter can be detected as a light point defect. An example(schematic configuration diagram) of a surface inspection deviceincluding such an incident system and light-receiving systems isillustrated in FIG. 1. In FIG. 1, although incident light isschematically illustrated with a solid-line arrow and radiation light isschematically illustrated with a dotted-line arrow, the incidencedirection and radiation direction illustrated in the figure areexemplary and shall not limit the present invention in any way.

A surface inspection device 10 illustrated in FIG. 1 includes: as anincident system and light-receiving systems,

a laser light source 100; and

low-angle side light receivers 101, 102 and a high-angle side lightreceiver 201 which receive the radiation light radiated by the lightincident from the laser light source 100 being scattered or reflected bythe surface (polished surface) of a polished wafer 1.

Although the surface inspection device 10 illustrated in FIG. 1 includesone high-angle side light receiver and two low-angle side lightreceivers, the surface inspection device is not limited to such aconfiguration and may include two high-angle side light receivers andone low-angle side light receiver. The light-receiving angles of the twolow-angle side light receivers may be the same or may differ. This maybe true also in the case where there are two high-angle side lightreceivers. Among these three light receivers, at least one selected fromthe group consisting of a light-receiving angle and polarizationselectivity differs from each other. This point will be furtherdescribed later. In the surface inspection device 10 illustrated in FIG.1, the low-angle side light receivers 101 and 102 receive the radiationlight in the whole circumference above a stage 11, but the configurationthereof is not limited to the one illustrated in FIG. 1 as far as it iscapable of receiving radiation light.

The surface inspection device 10 further includes a rotary motor 12 formaking the stage 11 on which the polished wafer 1 is to be placedrotatable, and movable means (not shown) for making the stage 11 movablein the horizontal direction, so that the irradiation position of thelight incident from each laser light source can be changed. Thus, it ispossible to sequentially irradiate (scan) an area or whole surface to beevaluated on the surface of the polished wafer 1 with light, and detectan abnormality in the area or whole surface to be evaluated.

The surface inspection device 10 further includes a controller 13configured to control the rotation and movement in the horizontaldirection of the stage 11, and a calculator 14 configured to calculate,on the basis of the information about the radiation light detected byeach light receiver, the detection size of a detected abnormality.Moreover, a PC (Personal Computer) 15 receives from the controller 13the position information about the position irradiated with light, andtransmits a signal for moving the stage 11 in order to irradiate anun-irradiated position with light. Furthermore, the PC 15 is capable ofreceiving, from the calculator 14, the information about the detectionsize of a detected abnormality, and generating the measurement result 1,the measurement result 2, and the measurement result 3.

However, the configuration of the surface inspection device illustratingthe outline in FIG. 1 is exemplary. In the above evaluation method, thesurface inspection device is not limited to the one with theconfiguration illustrated in FIG. 1, and various types of surfaceinspection devices can be used if each is a surface inspection deviceincluding one incident system and three light-receiving systems (firstlight-receiving system, second light-receiving system, and thirdlight-receiving system) among which at least one selected from the groupconsisting of a light-receiving angle and polarization selectivitydiffers from each other. For example, as the surface inspection deviceincluding one incident system and the above three light-receivingsystems, Surfscan series SP5 manufactured by KLA TENCOR Corporation canbe used.

<Abnormality to be Detected>

The object to be detected in the above evaluation method is anabnormality selected from the group consisting of a process-induceddefect and a surface-adhered foreign matter present on the abovepolished surface of a semiconductor wafer. These abnormalities aredetected as a light point defect in a light-receiving system bydirecting, from an incident system, light to the polished surface of apolished wafer to be evaluated and by the light being radiated(scattered or reflected) from the polished surface. By detecting thelight point defect, the calculator of the surface inspection device cancalculate, from the size of the detected light point defect and on thebasis of the size of a standard particle, the size (detection size) ofan abnormality causing the light point defect. The calculation of thedetection size on the basis of the size of a standard particle can beperformed by calculation means in a commercially available surfaceinspection device or with a known calculation method.

A surface-adhered foreign matter is a foreign matter which adhered inthe manufacturing process and/or the like of polished wafers, and isusually referred to as Particle.

In contrast, a process-induced defect is introduced into a polishedwafer due to a chemical or mechanical processing in the manufacturingprocess of polished wafers. Examples of the process-induced defectinclude:

PID (Polished Induced Defect) which is a linear convex defect introducedby polishing, such as in mirror polishing or in the rough polishing (forexample, lapping) usually performed before mirror polishing;

Short PID which is a relatively short island-shaped PID among PIDs; and

Shallow which is a relatively smooth concave shaped defect.

Specific Embodiment of Evaluation Method

Next, a specific embodiment of the above evaluation method will bedescribed.

(Incident System)

The wavelength of the incident light incident on the polished surface ofa polished wafer to be evaluated from one incident system is notparticularly limited. The incident light is ultraviolet light in anembodiment, but may be visible light or another light. Here, theultraviolet light in the present invention means the light in awavelength region less than 400 nm, while the visible light means thelight in a wavelength region from 400 to 600 nm.

The incident angle of the incident light incident on the polishedsurface of a polished wafer to be evaluated from one incident system maybe equal to or greater than 0° and equal to or less than 90° and ispreferably higher than 0° and less than 90° when all the directionshorizontal to the polished surface are defined as 0°, the directionperpendicular to the polished surface is defined as 90°, and theincident angle is defined as a range from 0° minimum to 90° maximum.

(Light-Receiving System)

As described above, the surface inspection device used in the evaluationmethod of the present invention includes three light-receiving systems,among which at least one selected from the group consisting of alight-receiving angle and polarization selectivity differs from eachother. In an embodiment, one light-receiving system is a high anglelight-receiving system which receives, on the high angle side, theradiation light from the polished surface of a polished wafer to beevaluated, while the other two light-receiving systems are low anglelight-receiving systems which receive, on the low angle side, the aboveradiation light. The light-receiving angles of two low anglelight-receiving systems may be the same or may be different. Here, thehigh angle (side)/low angle (side) relative to the light-receiving angleare relatively determined on the basis of a relationship between oneangle side and another angle side, and a specific angle shall not belimited. In an embodiment, when the angle is defined, as with theincident angle described earlier, on the basis of the polished surfaceof a polished wafer to be evaluated, the light reception on the highangle side may refer to the light reception with a light-receiving angleranging from higher than 80° to equal to or lower than 90°, and thelight reception on the low angle side may refer to the light receptionwith a light-receiving angle ranging from 0° to 80°. Moreover, inanother embodiment, two light-receiving systems may be high anglelight-receiving systems and one light-receiving system may be a lowangle light-receiving system. In this case, the light-receiving anglesof two high angle light-receiving systems may be the same or may bedifferent.

At least one selected from the group consisting of a light-receivingangle and polarization selectivity differs from each other among theabove three light-receiving systems. The light-receiving angle is asdescribed above. On the other hand, “polarization selectivity differs”means that at least one of a characteristic of selecting and receivingpolarized light (i.e., having polarization selectivity), acharacteristic of receiving omnidirectional light (i.e., having nopolarization selectivity), and a characteristic of selectively receivingpolarized light having a specific azimuth angle (or a specific range)among polarized lights differs among light-receiving systems. Means forimparting polarization selectivity to a light-receiving system iswell-known. For example, a light-receiving system with polarizationselectivity can be constituted by incorporating a polarization filter inthe light-receiving system, and a characteristic of selectivelyreceiving polarized light having a specific azimuth angle (or an azimuthangle in a specific range) can be imparted to the light-receiving systemaccording to the type of a polarization filter.

In the above surface inspection device, in an embodiment, onelight-receiving system can receive omnidirectional light, while theother two light-receiving systems can selectively receive polarizedlight. Moreover, in a specific embodiment, one light-receiving systemcan receive omnidirectional light, while the other two light-receivingsystems each can selectively receive polarized light having a differentazimuth angle. For two light-receiving systems which selectively receivepolarized light, when the azimuth angle of the polarized light receivedby one light-receiving system is designated by θ₁° and the azimuth angleof the polarized light received by another one is designated by θ₂°,0°≤θ₁°≤90° and 90°≤θ₂°≤180° can be satisfied. Furthermore, in apreferable specific embodiment, the light-receiving angle of thelight-receiving system which receives the omnidirectional light can be ahigher angle than the light-receiving angle of the light-receivingsystem which receives polarized light. The omnidirectional light isreferred to also as unpolarized light, and is the light which is notpolarized light. In contrast, the polarized light is the light having aspecific directivity (azimuth angle).

A more preferable specific embodiment of the light-receiving system isas follows:

the first light-receiving system receives omnidirectional light,

the second light-receiving system receives the polarized light havingazimuth angle θ₁°,

the third light-receiving system receives the polarized light havingazimuth angle θ₂°, and

the light-receiving angle of the first light-receiving system is ahigher angle than the light-receiving angles of the secondlight-receiving system and third light-receiving system.

That is, the first light-receiving system which receives theomnidirectional light is a high angle light-receiving system, while thesecond light-receiving system and third light-receiving system whichreceive polarized light are low angle light-receiving systems.Furthermore, the azimuth angles θ₁° and θ₂° of the polarized lightreceived by two light-receiving systems (the second light-receivingsystem and third light-receiving system) which receive polarized lightsatisfy θ₁°≤θ₂°.

The object to be detected in the above evaluation method is anabnormality selected from the group consisting of a process-induceddefect and a surface-adhered foreign matter present on a polishedsurface. Among these abnormalities, the surface-adhered foreign matter(usually referred to as “Particle”) tends to isotropically scatter theincident light incident from an incident system as compared with theprocess-induced defect. In other words, the process-induced defect tendsto anisotropically scatter the incident light incident from an incidentsystem as compared with the surface-adhered foreign matter. The presentinventor conceives that, regarding such tendency, in a surfaceinspection device with the light-receiving system according to the morepreferable specific embodiment described above, the secondlight-receiving system which receives polarized light having a lowerazimuth angle can suppress the reflected light component from a polishedwafer surface (polished surface), and can easily detect the scatteringlight from the surface-adhered foreign matter which isotropicallyscatters light. In contrast, the present inventor conceives that thethird light-receiving system which receives polarized light having ahigher azimuth angle has, as compared with the second light-receivingsystem, a lower effect of suppressing the reflected light component froma polished wafer surface (polished surface), but can detect, with highsensitivity, the scattering light from a process-induced defect whichanisotropically scatters light. Furthermore, the present inventorpresumes that, by combining the above second light-receiving system andthird light-receiving system with the first light-receiving system whichreceives the omnidirectional light on the higher angle side than thesetwo light-receiving systems, the detection sensitivity for various typesof abnormalities can be further increased. Thus, the present inventorconceives that both the process-induced defect and the surface-adheredforeign matter can be detected with high sensitivity. However, the abovediscussion includes the presumption of the present inventor and shallnot limit the present invention in any way.

As described earlier, since the causes of the process-induced defect andsurface-adhered foreign matter differ from each other, the means forreducing these process-induced defect and surface-adhered foreign matteralso differs from each other. For example, the surface-adhered foreignmatter can be usually removed by washing. Accordingly, the washing maybe enhanced in order to reduce the surface-adhered foreign matters. Onthe other hand, since the process-induced defect is introduced bypolishing or the like as described above, a change of the variousconditions in the manufacturing process is desirably considered in orderto reduce the process-induced defects. Accordingly, in the evaluation ofa polished wafer, the surface-adhered foreign matter and theprocess-induced defect can be desirably discriminated and detected. Thisis because, by discriminating and detecting, the number of occurrencesand/or presence state (distribution) of each of the surface-adheredforeign matter and process-induced defect can be grasped and thusappropriate reducing means can be selected in accordance with the numberof occurrences and/or distribution. In this context, with the surfaceinspection device provided with the light-receiving system according tothe above preferable embodiment, whether a detected abnormality is aprocess-induced defect or a surface-adhered foreign matter can bedetermined on the basis of the determination criteria selected from thegroup consisting of:

the presence or absence of detection and detection size in themeasurement result 1 obtained by the light reception with the firstlight-receiving system which receives, on the high angle side, theomnidirectional light;

the presence or absence of detection and detection size in themeasurement result 2 obtained by the light reception with the secondlight-receiving system which receives, on the low angle side, thepolarized light having azimuth angle θ₁°; and

the presence or absence of detection and detection size in themeasurement result 3 obtained by the light reception with the thirdlight-receiving system which receives, on the low angle side, thepolarized light having azimuth angle θ₂° (here θ₁°<θ₂°).

The present inventor conceives that the reason why such determination isenabled is that the process-induced defect and surface-adhered foreignmatter each have a different behavior in scattering and reflecting lightdue to a difference in the shape and the like caused by a difference incauses and therefore the presence or absence of detection and/ordetection size differ among the light-receiving systems each having adifferent light-receiving angle and/or polarization selectivity.

With the surface inspection device provided with the light-receivingsystem according to the preferable embodiment described above, whether adetected abnormality is a surface-adhered foreign matter or aprocess-induced defect can be more preferably determined on the basis ofthe criteria shown in Table 1 below. In Table 1 below, X satisfies1.0<X<2.0. The present inventor conceives that the reason why aprocess-induced defect and surface-adhered foreign matter can bediscriminated by X which satisfies 1.0<X<2.0 of a relational formulabelow and the criteria below based on the presence or absence ofdetection in a specific light-receiving system is due to a difference ofthe light-receiving angle and/or polarization selectivity of eachlight-receiving system and also due to a difference in the behavior,between a process-induced defect and a surface-adhered foreign matter,in scattering and reflecting light. This point is a new insight obtainedby the intensive study of the present inventor and conventionally notknown in any way.

TABLE 1 Types of abnormalities Determination criteria Surface-adhereddetected only in measurement result 2, and not foreign matter detectedin measurement result 1 and measurement result 3, satisfies (detectionsize in measurement result 3)/(detection size in measurement result 2) <X, or satisfies (detection size in measurement result 1)/(detection sizein measurement result 2) < X Process-induced detected in at least one ofmeasurement result 1 and defect measurement result 3, and not detectedin measurement result 2, satisfies (detection size in measurement result3)/(detection size in measurement result 2) ≥ X, or satisfies (detectionsize in measurement result 1)/(detection size in measurement result 2) ≥X

The X satisfies 1.0<X<2.0, and preferably 1.3<X<1.6. As an example,X=1.4 is established, for example.

A more specific embodiment of the above evaluation method will bedescribed later on the basis of Examples. With the evaluation by theabove evaluation method, various types of evaluations on abnormalities,such as the presence or absence of an abnormality on the surface of apolished wafer and the existing number and/or existing position(distribution) of abnormalities, can be performed.

The evaluation can be performed by the above-described evaluationmethod, and then on the basis of the obtained evaluation results,process changes and/or maintenances (for example, a change inmanufacturing conditions, replacement of manufacturing devices, washing,improvement of quality of chemical liquid, and the like.) for reducingvarious types of abnormalities can be performed on the manufacturingprocess of polished wafers, so that a high-quality polished wafer withless abnormalities can be subsequently provided as a product wafer.

Moreover, a polished wafer before being shipped as a product can beevaluated by the above evaluation method, and a polished wafer, in whichthe existing number of various types of abnormalities has been confirmedto fall within a predetermined allowable range (to be equal to or lessthan a threshold), can be shipped as a product wafer, so that ahigh-quality polished wafer can be stably supplied. The threshold is notlimited in particular, and can be appropriately set in accordance withthe application and/or the like of a product wafer.

That is, the above evaluation method can be used for the process controland/or quality control of polished wafers.

[Polished Wafer]

A further aspect of the present invention relates to a semiconductorwafer (polished wafer) which has a polished surface and has beenevaluated by the above evaluation method. Such a polished wafer can be apolished wafer, in which the existing number of various types ofabnormalities has been confirmed, by evaluation based on the aboveevaluation results, to fall within a predetermined allowable range (tobe equal to or less than a threshold).

EXAMPLES

Hereinafter, the present invention will be further explained on thebasis of Examples. However, the present invention is not limited to theembodiments shown in the Examples.

1. Detection of Light Point Defect (LPD) and Calculation of Size ofAbnormality

A polished wafer to be evaluated was prepared, and a light point defectwas detected using a Surfscan Series SP5 manufactured by KLA TENCORCorporation as the surface inspection device. The Surfscan Series SP5manufactured by KLA TENCOR Corporation includes, as one incident system,an ultraviolet light source to cause incident light to be obliquelyincident on the surface of a wafer to be evaluated, and includes, aslight-receiving systems, three light-receiving systems called a DNO(Dark-Field Narrow Oblique) channel, a DW1O (Dark-Field Wide 1 Oblique)channel, and a DW2O (Dark-Field Wide 2 Oblique) channel. DNO is alight-receiving system which receives omnidirectional light (i.e.,without polarization selectivity), and is a light-receiving system onthe high angle side relative to the DW1O channel and DW2O channel. Onthe other hand, the DW1O channel and DW2O channel are light-receivingsystems on the low angle side relative to the DNO channel, and havepolarization selectivity. The azimuth angle of the polarized lightreceived by the DW1O channel is lower than the azimuth angle of thepolarized light received by the DW2O channel. The azimuth angle of thepolarized light received by the DW1O channel is equal to or greater than0° and is equal to or less than 90°, while the azimuth angle of thepolarized light received by the DW2O channel is equal to or greater than90° and is equal to or less than 180°.

Using the surface inspection device Surfscan Series SP5 manufactured byKLA TENCOR Corporation, the whole polished surface of a polished waferto be evaluated was scanned with incident light to detect an abnormalityas a light point defect (LPD), and then on the basis of the size of thelight point defect, the detected abnormality size (detection size) wascalculated by a calculator in the above surface inspection device. Thelower limit (lower limit of detection) of the size of a light pointdefect detected in each light-receiving system of the above surfaceinspection device is 36 nm in the DNO channel, 19 nm in the DW1Ochannel, and 31 nm in the DW2O channel.

2. Observation of Abnormality with Scanning Electron Microscope

The polished surface of the polished wafer evaluated in the above item 1was observed with a scanning electron microscope (SEM), and anabnormality present at the position of the light point defect detectedby the above surface inspection device was classified into asurface-adhered foreign matter (Particle) and various types ofprocess-induced defects (PID, Short PID, and Shallow) on the basis ofthe observed shape. An example (SEM image) of each abnormality observedwith the SEM is shown in FIG. 2. FIG. 2(a), FIG. 2(b), FIG. 2(c), andFIG. 2(d) are SEM images of abnormalities classified as Particle, asPID, as Short PID, and as Shallow, respectively.

3. Study on Calculated Size and Type of Abnormality

(1) Comparison between the result obtained in the DW1O channel and theresult obtained in the DW2O channel

FIG. 3 illustrates a graph, in which for each abnormality classified onthe basis of the observation by the SEM in the above item 2, theabnormality size calculated from the size detected as a light pointdefect in the DW1O channel and the abnormality size calculated from thesize detected as a light point defect in the DW2O channel in the aboveitem 1 are plotted. In this graph, abnormalities plotted on the X-axisare abnormalities detected only in the DW1O channel and not detected inthe DW2O channel, while LPDs plotted on the Y-axis are abnormalitiesdetected only in the DW2O channel and not detected in the DW1O channel.

The following tendencies can be confirmed from the graph illustrated inFIG. 3.

(i) Particle is:

detected only in the DW1O channel (not detected in the DW2O channel), orthe size ratio DW20/DW1O is approximately 1 (present mainly on the lineof y=x or in the periphery thereof);

(ii) PID, Short PID, and Shallow are:

detected only in the DW2O channel (not detected in the DW1O channel), orthe size ratio DW20/DW1O is approximately 2 (present mainly on the lineof y=2x or in the periphery thereof).

(2) Comparison Between the Result Obtained in the DW1O Channel and theResult Obtained in the DNO Channel

FIG. 4 illustrates a graph, in which for each abnormality classified onthe basis of the observation by the SEM in the above item 2, theabnormality size calculated from the size detected as a light pointdefect in the DW1O channel and the abnormality size calculated from thesize detected as a light point defect in the DNO channel in the aboveitem 1 are plotted. In this graph, abnormalities plotted on the X-axisare abnormalities detected only in the DW1O channel and not detected inthe DNO channel, while abnormalities plotted on the Y-axis are LPDsdetected only in the DNO channel and not detected in the DW1O channel.

The following tendencies can be confirmed from the graph illustrated inFIG. 4.

(i) Particle is:

detected only in the DW1O channel (not detected in the DNO channel), or

the size ratio DNO/DW1O is approximately 1 (present mainly on the lineof y=x or in the periphery thereof);

(ii) PID, Short PID, and Shallow are:

detected only in the DNO channel (not detected in the DW1O channel), or

the size ratio DNO/DW1O is approximately 2 (present mainly on the lineof y=2x or in the periphery thereof).

As shown in FIG. 3 and FIG. 4, among various types of abnormalities,there is a difference in the size calculated from size of the detectedlight point defect in the above three light-receiving systems and/or inthe presence or absence of detection.

Then, on the basis of the above results, the abnormality discriminationconditions shown in Table 2 below were prepared. Since the DW20/DW1Osize ratio and DNO/DW1O size ratio of Particle are approximately 1 aswell as the DW20/DW1O size ratio and DNO/DW1O size ratio of theprocess-induced defects, such as a PID, are approximately 2, it waspresumed that the thresholds of the DW20/DW1O size ratio and DNO/DW1Osize ratio were desirably set to greater than 1.0 and less than 2.0, forthe discrimination of Particles and the process-induced defect. Thus,they were provisionally set to 1.4. Discrimination was performed usingthe abnormality determination criteria shown in Table 2, and thevalidity of the abnormality determination criteria was confirmed by theresults of observation by SEM in the above item 2. As the results, therewere extremely few abnormalities not compliant with the abnormalitydetermination criteria shown in Table 2, and the compliant ratiocalculated by “compliant ratio (%)=[number of compliantabnormalities/(number of compliant abnormalities+number of un-compliantabnormalities)]×100” was higher than 90% as shown in Table 2.

TABLE 2 Number of Number of abnormalities abnormalities compliant withnot compliant with Compliant Abnormality determination criteriaDetermination determination criteria determination criteria ratiodetected only in DW1O channel (not Particle 199 2 99% detected in DW2Ochannel and in DNO channel), size ratio DW2O/DW1O < 1.4 size ratioDNO/DW1O < 1.4 detected in DW2 channel and/or PID 53 2 96% DNOchannel(not detected in DW1O Short PID channel) Shallow size ratioDW2O/DW1O ≥ 1.4 size ratio DNO/DW1O ≥ 1.4

An aspect of the present invention is useful in the field ofmanufacturing polished wafers.

1. A method of evaluating a semiconductor wafer, which has a polishedsurface, by using a laser surface-inspection device comprisinglight-incident and light-receiving systems, the method comprising:evaluating the semiconductor wafer by detecting, as a light pointdefect, an abnormality selected from the group consisting of aprocess-induced defect and a surface-adhered foreign matter present onthe polished surface of the semiconductor wafer, on the basis ofmeasurement result 1 obtained by directing incident light to thepolished surface of the semiconductor wafer from one light-incidentsystem and receiving, with a first light-receiving system, radiationlight which has been radiated by the incident light being reflected orscattered by the polished surface, measurement result 2 obtained byreceiving the radiation light with a second light-receiving system, andmeasurement result 3 obtained by receiving the radiation light with athird light-receiving system; and determining whether the detectedabnormality is a process-induced defect or a surface-adhered foreignmatter, on the basis of a determination criteria selected from the groupconsisting of presence or absence of detection and detection size in themeasurement result 1, presence or absence of detection and detectionsize in the measurement result 2, and presence or absence of detectionand detection size in the measurement result 3, wherein: the firstlight-receiving system receives omnidirectional light, the secondlight-receiving system receives polarized light having a first azimuthangle designated by θ₁°, the third light-receiving system receivespolarized light having a second azimuth angle designated by θ₂°different from the first azimuth angle θ₁°, the light-receiving angle ofthe first light-receiving system is larger than light-receiving anglesof the second light-receiving system and third light-receiving system,and at least one selected from the group consisting of a light-receivingangle and polarization selectivity differs among the firstlight-receiving system, the second light-receiving system, and the thirdlight-receiving system.
 2. The method of evaluating according to claim1, wherein θ₁° satisfies 0°≤θ₁°≤90° and θ₂° satisfies 90°≤θ₂°≤180°. 3.The method of evaluating according to claim 1, which comprisesperforming the determination according to the following criteria: Typesof abnormalities Determination criteria Surface-adhered detected only inmeasurement result 2, and not foreign matter detected in measurementresult 1 and measurement result 3, satisfies [(detection size inmeasurement result 3)/(detection size in measurement result 2)] < X, orsatisfies [(detection size in measurement result 1)/(detection size inmeasurement result 2)] < X Process-induced detected in at least one ofmeasurement result 1 and defect measurement result 3, and not detectedin measurement result 2, satisfies (detection size in measurement result3)/[(detection size in measurement result 2) ≥ X], or satisfies(detection size in measurement result 1)/[(detection size in measurementresult 2) ≥ X]

wherein 1.0<X<2.0 is satisfied.
 4. The method of evaluating according toclaim 3, wherein X satisfies 1.3<X<1.6.
 5. The method of evaluatingaccording to claim 1, wherein the incident angle of the incident lightis higher than 0° and less than 90° when all directions parallel to thepolished surface of the semiconductor wafer are defined as 0° and adirection perpendicular to the polished surface is defined as 90°.
 6. Asemiconductor wafer, which has a polished surface and has been evaluatedby the method of evaluating according to claim 1.